The freezer offers enough room for four five-gallon Cornelius kegs. [Matt] salvaged the weight sensors from some cheap bathroom scales and rigged them up with some plywood discs to serve as the base for each keg. After working out the electronics to reliably read from the sensors (which was no small job) he hooked them up to a microcontroller and a touch screen. As you can see in the video after the break, the system calculates the number of pints left in each keg based on its weight. This can be easily calibrated using the touch screen.